1. Field of the Invention
The invention relates to a LED lamp and color mixing optics to produce a uniform intensity distribution and a uniform color output throughout the beam pattern of the light beam produced by a multi-color LED light source for use in LED lamps.
2. Description of Relevant Art
Color LED lamps should have an even intensity and color distribution over a broad range of radiation angles. As there is no single point LED source available, the radiation of multiple LED sources must be combined to form a multi-color light source. These multiple LED sources are placed offset to each other, so there is no common focal point. To obtain an even color distribution, color mixing is required.
Conventional color mixing uses light guides which typically are large and inefficient. The rule of thumb for a light guide is that it should be about 10 times longer than the dimensions of the multi-color light source. A typical 90 Watt halogen lamp produces about 1200 lumens. An array of many large LEDs is necessary to produce such output light. Such 1200 lumen output arrays may be about 5-6 mm in diameter. If such a light source comprises multi-color LEDs, a 50-60 mm light guide would be needed to properly mix the colors. Considering that the beam needs to be shaped after color mixing, the dimensions needed for a light guide become too large to fit into conventional lamp housings.
U.S. Pat. No. 8,529,102 discloses a reflector system for a multi-color LED lamp providing color mixing. The system uses two reflective surfaces to redirect the light before it is emitted.
A lens the system with multiple curved surfaces for a multi-color LED lamp is disclosed in the U.S. Pat. No. 8,733,981. It is based on a total inner reflection (TIR) lens system which has some similarity to a Fresnel lens.